Re: [Boost-users] [asio] sync operations with timeout

Subject: Re: [Boost-users] [asio] sync operations with timeout
From: Igor R (boost.lists_at_[hidden])
Date: 2011-08-30 10:03:43

> I write network library which offers blocking socket operations (connect, read,
> write, ...) with timeouts, using boost::asio asynchronous operations as
> implementation. It is actually some sort of wrapper around boost::asio.
> Implementation does something like this (read, for example):
>
> do_read()
> {
> Â  Â  Â  Â timer.async_wait(&handle_timer)
> Â  Â  Â  Â socket.async_read(..., handle_read);
> Â  Â  Â  Â wait_for_all_handlers();
> Â  Â  Â  Â deal_with_ec();
> }
>
> handle_timer() { socket.cancel(); }
> handle_read() { timer.cancel(); }
>
> I have one io_service for all the sockets/timers with one thread doing
> io_service::run(). Code is multithreaded, so many threads run that functions
> like do_read() simultaneously (for different sockets, of course).
>
> I have two questions:
>
> 1. How to wait for completion of all handlers? Currently I use shared_ptr with
> mutex+condvar (for each library call), it works fine, but seems to be too
> heavy-weight.
>
> 2. There is a chance (with small timeouts), that timer expires before
> async_read() is started, so sock.cancel() is no-op in handle_timer(), and timer
> will be disabled. Currently, I just ignore this. I can use another mutex (or
> strand) to protect from this, but it is also heavy-weight.

It probably isn't an answer to your questions, but perhaps you'll find
the following approach useful:
http://lists.boost.org/Archives/boost/2007/04/120339.php